Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx> wrote:
> On Wed, May 15, 2013 at 02:33:36PM +0200, Florian Westphal wrote:
> > > + const struct xt_tcpoptstrip_target_info *info = par->targinfo;
> > > unsigned int optl, i, j;
> > > struct tcphdr *tcph;
> > > u_int16_t n, o;
> > > u_int8_t *opt;
> > > + int len;
> > > +
> > [..]
> > > + len = skb->len - tcphoff;
> > > + if (len < sizeof(struct tcphdr))
> >
> > I think this needs a cast 'if (len < (int) sizeof( ...?
>
> I'm not hitting any compilation warning.
len is signed, thats why i asked, and, afair recall sizeof
is unsigned and thus len is treated as unsigned.
Test program yields:
#include <stdio.h>
#include <stdlib.h>
int main (int argc, char *argv[])
{
char foo[20];
int len = atoi(argc > 1 ? argv[1] : "0");
if (len < sizeof(foo))
printf("%d lt %lu\n", len, sizeof(foo));
else
printf("%d ge %lu\n", len, sizeof(foo));
return 0;
}
t.c: In function 'main':
t.c:7:10: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
./t -42
-42 ge 20
gcc version 4.6.3.
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